Fast valve actuation system for an automatic transmission

ABSTRACT

A fast valve actuation system for an automatic vehicle transmission includes a pair of spring-biased shift valves. Solenoids control the application of pressurized hydraulic fluid to the head of each of the shift valves. Each shift valve has at least one port that is coupled to a fluid chamber of a torque transferring mechanism of an automatic transmission. The position of each of the shift valves determines whether its ports are connected with fluid pressure. Fluid passages connect the head of each shift valve to the spring pocket of the other shift valve.

This application is a continuation application of U.S. application Ser.No. 12/943,322, entitled “FAST VALVE ACTUATION SYSTEM FOR AN AUTOMATICTRANSMISSION,” which was filed on Nov. 10, 2010, and which claimspriority to U.S. Provisional Patent Application Ser. No. 61/287,003,filed Dec. 16, 2009, the entirety of both of which is incorporatedherein by reference.

TECHNICAL FIELD

This disclosure relates generally to automatic transmissions, and moreparticularly, to an electro-hydraulic fast valve actuation system for anautomatic transmission.

BACKGROUND

In vehicles with automatic transmissions, a torque converter or othertype of fluidic coupling transfers torque from the vehicle engine (orother drive unit) to the transmission. Rather than requiring the vehicleoperator to engage in manual gear-shifting, automatic transmissions havean on-board control system that can automatically control changes in thegear ratio once the vehicle is shifted into a forward or reverse rangeby the operator.

The on-board control system includes electro-hydraulic components. Thehydraulic components include valving and fluid passages that directpressurized hydraulic fluid to clutches to be applied and drainhydraulic fluid from clutches to be released, in response to electricalsignals received from an electronic control unit.

The electro-hydraulic controls often include directional control valves,also known as shift valves or logic valves. The shift valves have portsthat are coupled to fluid chambers of the transmission clutches. Whenthe shift valves change position, ports on the valves are opened orclosed as needed to direct pressurized hydraulic fluid to theappropriate clutches or other destination.

A solenoid often controls the changes in position of a shift valve. Thesolenoid receives electrical signals from the electronic control unitand outputs fluid pressure to the shift valve in response to theelectrical signals. The fluid pressure output by the solenoid strokesthe shift valve if the amount of pressure is sufficient to overcome thebiasing force of the shift valve's return spring.

When the position of the shift valve changes, a clutch's fluid chambermay be connected to, or disconnected from, a source of pressurizedhydraulic fluid. If the position of the shift valve connects a clutch tofluid pressure, the clutch is applied. The clutch is released if theposition of the shift valve causes the clutch to be disconnected fromthe source of fluid pressure.

The electro-hydraulic controls also typically include pressure controlvalves, which may be known as trim valves. A trim valve controls therate at which fluid pressure is applied to the clutch to which the trimvalve is coupled (e.g. directly or via a shift valve). The trim valvethus controls how slowly or quickly the clutch connected to the trimvalve is applied or released.

SUMMARY

According to one aspect of this disclosure, an electro-hydraulic controlfor an automatic transmission includes a first shift valve axiallytranslatable in a first valve chamber of a hydraulic control circuit foran automatic transmission. The first shift valve has a first valve head,a first spool, a first plurality of axially-spaced lands defining aplurality of ports on the first shift valve, at least one of the portsbeing in fluid communication with a first torque transferring mechanismof the automatic transmission, and a first spring chamber axially spacedfrom the first valve head. The control also includes a firstelectro-hydraulic actuator having a first output in fluid communicationwith the first shift valve, and a second shift valve axiallytranslatable in a second valve chamber of the hydraulic control circuit.The second shift valve includes a second valve head, a second spool, asecond plurality of axially-spaced lands defining a plurality of portson the second shift valve, at least one of the ports being in fluidcommunication with a second torque transferring mechanism of theautomatic transmission, and a second spring chamber axially spaced fromthe second valve head. The control also includes a secondelectro-hydraulic actuator having a second output in fluid communicationwith the second shift valve, a first passage fluidly coupling the firstvalve head and the second spring chamber to the first output, and asecond passage fluidly coupling the second valve head and the firstspring chamber to the second output.

The first electro-hydraulic actuator may be actuatable by an electroniccontrol unit to output fluid pressure to the head of the first shiftvalve and the spring chamber of the second shift valve at substantiallythe same time. The second electro-hydraulic actuator may similarly beactuatable by the electro-hydraulic control actuator to output fluidpressure to the head of the second shift valve and the spring chamber ofthe first shift valve at substantially the same time.

The control may include a first pressure control valve selectivelycoupled to the first torque transferring mechanism through a port of thefirst shift valve and a second pressure control valve selectivelycoupled to the second torque transferring mechanism through a port ofthe second shift valve. The control may include a third fluid passageselectively coupling the first port of the first shift valve to a thirdpressure control valve. The third fluid passage may selectively couplethe second torque transferring mechanism to the third pressure controlvalve through the second shift valve.

The first shift valve may include a first land adjacent the first valvehead and a second land axially spaced from the first land to define afirst port, wherein the first torque transferring mechanism is coupledto the first port. The first spring chamber may be axially spaced fromthe second land.

The first and second shift valves may be fluidly coupled to pressurecontrol valves to permit the first and second torque transferringmechanisms to be connected to fluid pressure at the same time. The firstand second electro-hydraulic actuators may be independently actuatableto permit one of the first and second torque transferring mechanisms tobe connected to fluid pressure while the other of the first and secondtorque transferring mechanisms is not connected to fluid pressure. Insome embodiments, the first and second torque transferring mechanismsmay be clutches. In some embodiments, the first and second torquetransferring mechanisms may be opposing sides of a variator diskactuator.

The first and second passages may prevent the first and second shiftvalves from stroking at the same time. In some embodiments, the firstand second passages may supply fluid pressure to sequentially stroke oneof the first and second shift valves and destroke the other of the firstand second shift valves in less than about 0.08 seconds.

According to another aspect of this disclosure, an automatictransmission includes a variable ratio unit to transfer torque from avehicle drive unit to a transmission output shaft, and a hydrauliccircuit fluidly coupled to the variable ratio unit. The hydrauliccircuit includes a first fluid chamber pressurizable to apply a firsttorque transferring mechanism of the variable ratio unit, a second fluidchamber pressurizable to apply a second torque transferring mechanism ofthe variable ratio unit, a first shift valve fluidly coupled to thefirst fluid chamber to selectively direct fluid pressure to the firstfluid chamber, and a second shift valve fluidly coupled to the secondfluid chamber to selectively direct fluid pressure to the second fluidchamber. The first and second shift valves are in fluid communicationwith each other to connect one of the first and second fluid chambers tofluid pressure and disconnect the other of the first and second fluidchambers from fluid pressure in rapid succession.

Each of the first and second shift valves may have a valve head and aspring chamber axially spaced from the valve head, where the hydrauliccircuit includes a first passage fluidly coupling the valve head of thefirst shift valve with the spring chamber of the second shift valve anda second passage fluidly coupling the valve head of the second shiftvalve with the spring chamber of the first shift valve. In someembodiments, the first and second passages do not intersect with eachother.

The automatic transmission may include a first electro-hydraulicactuator fluidly coupled to the valve head of the first shift valve anda second electro-hydraulic actuator fluidly coupled to the valve head ofthe second shift valve, where the first electro-hydraulic actuator isactuatable by electrical signals to substantially simultaneously outputfluid pressure to the valve head of the first shift valve and the firstpassage. The first and second shift valves may be configured to permitboth of the first and second fluid chambers to be connected to fluidpressure at the same time. In some embodiments, the first and secondtorque transferring mechanisms may be clutches. In some embodiments, thefirst and second torque transferring mechanisms may be variator diskactuators in a continuously variable ratio transmission.

According to a further aspect of this disclosure, a valve actuationmethod for an automatic transmission includes detecting a change intorque direction, and stroking the first shift valve and destroking thesecond shift valve in rapid succession in response to the detectedchange in torque direction.

Patentable subject matter may include one or more features orcombinations of features shown or described anywhere in this disclosureincluding the written description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description refers to the following figures in which:

FIGS. 1-3 are schematic representations of different states of a fastvalve actuation system for an automatic transmission;

FIG. 4 is a graph depicting experimental data relating to the stroke anddestroke times of the valves depicted in FIGS. 1-3;

FIG. 5A is a schematic showing the fast valve actuation system of FIGS.1-3 in the context of an exemplary vehicle transmission;

FIG. 5B is a partially schematic simplified side view of a portion of avariator suitable for use in the transmission of FIG. 5A;

FIG. 5C is a simplified top view of the variator of FIG. 5B, withportions omitted for clarity; and

FIG. 6 is a schematic showing the fast valve actuation system of FIGS.1-3 in the context of a hydraulic control circuit for the transmissionof FIGS. 5A-5C.

In figures that depict schematic illustrations, the components may notbe drawn to scale, and lines shown as connecting the various blocks andcomponents shown therein represent connections which, in practice, mayinclude one or more electrical, mechanical and/or fluid connections,passages, communication links, couplings or linkages, as will beunderstood by those skilled in the art and as described herein. Ingeneral, like structural elements on different figures refer toidentical or functionally similar structural elements.

DETAILED DESCRIPTION

Aspects of this disclosure are described with reference to illustrativeembodiments shown in the accompanying drawings and described herein.While the present invention is described with reference to theseillustrative embodiments, it should be understood that the presentinvention as claimed is not limited to the disclosed embodiments. Forexample, while certain aspects of this disclosure are discussed hereinin the context of a continuously variable transmission, it will beunderstood by those skilled in the art that aspects of the presentdisclosure are applicable to other types and configurations of automatictransmissions.

As shown in FIGS. 1-3, a fast valve actuation system 48 includes a pairof shift valves 50, 52. Each of the shift valves 50, 52 resides in avalve chamber of a valve body of an electro-hydraulic control system foran automatic transmission. The shift valves 50, 52 are axially movablebetween destroked and stroked positions in their respective valvechambers.

The shift valve 50 selectively directs fluid pressure to a fluid chamberS1 of a torque transferring mechanism 140 of the automatic transmission.The shift valve 52 selectively directs fluid pressure to another fluidchamber S2 of a torque transferring mechanism 142 of the automatictransmission. The torque transferring mechanisms 140, 142 may beclutches, brakes, variator disk actuators, or the like, in accordancewith the particular design of the automatic transmission.

The shift valve 50 includes a valve head 82, a spring pocket 86, and anumber of axially-spaced lands 144, 146, 148 therebetween. The lands144, 146, 148 define ports 94, 96. The spring pocket 86 contains areturn spring 164, which biases the shift valve 50 in the destrokedposition shown in FIG. 1.

Similarly, the shift valve 52 includes a valve head 84, a spring pocket88, and a number of axially-spaced lands 150, 152, 154 therebetween. Thelands 150, 152, 154 define ports 98, 100. The spring pocket 88 containsa return spring 166, which biases the shift valve 52 in the destrokedposition shown in FIG. 1.

The shift valve 50 is fluidly coupled to an electro-hydraulic actuator108 by an output passage 156. A source of pressurized hydraulic fluid 54feeds fluid pressure to the electro-hydraulic actuator 108 through afluid passage 160. The electro-hydraulic actuator 108 selectivelyoutputs the fluid pressure to either the output passage 156 or to anexhaust chamber 106, in response to electrical signals issued by anelectronic control unit 16. An example of the electronic control unit 16is shown schematically in FIG. 5.

In the illustrations, the electro-hydraulic actuator 108 is anormally-low, on-off solenoid valve. When the electro-hydraulic actuator108 receives electrical input (i.e. current or voltage) from theelectronic control unit 16 (i.e., the electro-hydraulic actuator 108 is“actuated”), the electro-hydraulic actuator 108 outputs fluid pressurefrom the passage 160 to the output passage 156. In the absence ofelectrical input, the electro-hydraulic actuator 108 directs fluidpressure from the passage 156 to the exhaust chamber 106. When theelectro-hydraulic actuator 108 is actuated, fluid pressure applied tothe valve head 82 via the output passage 156 strokes the shift valve 50as shown in FIG. 2.

The electro-hydraulic actuator 108 includes an orifice 116 incommunication with the passage 160 and an orifice 120 in communicationwith the exhaust chamber 106. The orifices 116, 120 moderate the rate offluid flow through the fluid passages 160, 106, respectively, to controlthe rate at which pressure in the fluid passage changes.

In a similar fashion to shift valve 50, the shift valve 52 is fluidlycoupled to an electro-hydraulic actuator 110 by an output passage 158.The source of pressurized hydraulic fluid 54 feeds fluid pressure to theelectro-hydraulic actuator 110 through a fluid passage 162. Theelectro-hydraulic actuator 110 selectively connects fluid passage 158 toeither the feed passage 162 or to an exhaust passage 106, in response toelectrical signals issued by the electronic control unit 16.

In the illustrations, the electro-hydraulic actuator 110 is anormally-low, on-off solenoid valve. When the electro-hydraulic actuator110 receives electrical input from the electronic control unit 16 (i.e.,the electro-hydraulic actuator 110 is “actuated”), the electro-hydraulicactuator 110 outputs fluid pressure from the passage 162 to the outputpassage 158. In the absence of electrical input, the electro-hydraulicactuator 110 directs fluid pressure from the passage 158 to an exhaustchamber 106. When the electro-hydraulic actuator 110 is actuated, fluidpressure applied to the valve head 84 via the output passage 158 strokesthe shift valve 52 as shown in FIG. 3.

The electro-hydraulic actuator 110 includes an orifice 114 incommunication with the passage 162 and an orifice 118 in communicationwith the exhaust chamber 106. The orifices 114, 118 operate similarly tothe orifices 116, 120.

As shown in FIGS. 1-3, the port 94 of the shift valve 50 is in fluidcommunication with the fluid chamber S1 of the torque transferringmechanism 140 both when the shift valve 50 is destroked and when theshift valve 50 is stroked. Similarly, the port 98 of the shift valve 52is in fluid communication with the fluid chamber S2 of the torquetransferring mechanism 142 both when the shift valve 52 is destroked andwhen the shift valve 52 is stroked.

A number of pressure control (or “trim”) systems 60, 62, and 112 areselectively in fluid communication with the fluid chambers S1, S2,depending upon the position of the shift valves 50, 52. The trim system60 is configured to control the application of fluid pressure to thefluid chamber S1 when the shift valve 50 is destroked. The trim system62 is configured to control the application of fluid pressure to thefluid chamber S2 when the shift valve 52 is destroked. In theillustrations, each of the trim systems 60, 62, 112 includes avariable-bleed solenoid valve or a similar device that outputs fluidpressure in proportion to electrical input.

When the shift valve 50 is stroked, the port 94 is disconnected from thetrim system 60 and is fluidly coupled to a third trim system 112 asshown in FIG. 2. Similarly, when the shift valve 52 is stroked, the port98 is disconnected from the trim system 62 and is fluidly coupled to thethird trim system 112, as shown in FIG. 3. The selective blocking of thetrim systems 60, 62 and the use of the trim system 112 are the subjectof U.S. Provisional Patent Application Ser. No. 61/286,974, filed Dec.16, 2009, which is incorporated herein by this reference in itsentirety.

The ports 96, 100 of the shift valves 50, 52, are in fluid communicationwith pressure switches 102, 104, respectively. The pressure switches102, 104 detect changes in state of the shift valves 50, 52. When theshift valve 50 is stroked, the source of pressurized fluid 54 feedsfluid pressure to the port 96 via a fluid passage 168. The fluidpressure in the port 96 activates the pressure switch 102 and causes thepressure switch 102 to send an electrical signal to the electroniccontrol unit 16. Similarly, when the shift valve 52 is stroked, thesource of pressurized fluid 54 feeds fluid pressure to the port 100. Thefluid pressure in the port 100 activates the pressure switch 104 andcauses the pressure switch 104 to send an electrical signal to theelectronic control unit 16. An application of the pressure switches 102,104 for diagnostic purposes is the subject of U.S. Provisional PatentApplication Ser. No. 61/286,984, filed Dec. 16, 2009, which isincorporated herein by this reference in its entirety.

The fast valve actuation system 48 also includes a pair ofnon-intersecting fluid passages 90, 92. The fluid passage 90 couples theoutput passage 156 of the electro-hydraulic actuator 108 to valve head82 of the shift valve 50 and the spring pocket 88 of the shift valve 52.The fluid passage 92 couples the output passage 158 of theelectro-hydraulic actuator 110 to the valve head 84 of the shift valve52 and the spring pocket 86 of the shift valve 50.

In operation, when the electro-hydraulic actuator 108 is actuated (FIG.2), fluid pressure is output to the valve head 82 of the shift valve 50and to the spring pocket 88 of the shift valve 52 at the same time, orat nearly the same time, as indicated by the arrows 122, 124. The flowof pressurized fluid to the spring pocket 88 of the shift valve 52causes the shift valve 52 to destroke in a shorter amount of time thanif the shift valve 52 were allowed to destroke normally (i.e., by simplyallowing the fluid pressure at the valve head 84 to drain to the exhaustpassage 106).

Likewise, when the electro-hydraulic actuator 110 is actuated (FIG. 3),fluid pressure is output to the valve head 84 of the shift valve 52 andto the spring pocket 86 of the shift valve 50 at the same time, or atnearly the same time, as indicated by the arrows 126, 128. The flow ofpressurized fluid to the spring pocket 86 increases the speed at whichthe shift valve 50 destrokes, so that the shift valve 50 destrokes in ashorter amount of time than if the shift valve 50 were allowed todestroke normally. If both of the electro-hydraulic actuators 108, 110are actuated at the same time (e.g., if one of the electro-hydraulicactuators 108, 110 is actuated, or remains actuated, in error) the fluidpressure directed to the spring pockets 86, 88 via the fluid passages92, 90 prevents the shift valves 50, 52 from both stroking at the sametime, resulting in a valve state that looks similar to FIG. 1. In otherwords, each one of the shift valves 50, 52 can only be stroked one at atime. Applying the electro-hydraulic actuators 108, 110 simultaneouslyresults in the destroking of the shift valves 50, 52 rather than thestroking of both valves as would normally be the case.

Thus, the fast valve actuation system 48 only has three possible states:a “00” state in which both of the shift valves 50, 52 are destroked, a“10” state in which the shift valve 50 is stroked and the shift valve 52is prevented from stroking, and a “01” state in which the shift valve 50is prevented from stroking and the shift valve 52 is stroked. Actuationof only one of the electro-hydraulic actuators 108, 110 is required to,in rapid succession, stroke one of the shift valves 50, 52 and destrokethe other of the shift valves 50, 52. Additionally, actuation of onlyone of the electro-hydraulic actuators 108, 110 simultaneously causesone of the shift valves 50, 52 to stroke and the other of the shiftvalves 50, 52 to be blocked from stroking.

During a transition from the “10” state to the “01” state, the solenoid110 is actuated and the solenoid 108 is deactuated. As a result, thespring pocket 86 of the shift valve 50 is pressurized at the same time(or nearly the same time) that the valve head 82 is being exhausted.Also, the valve head 84 of the shift valve 52 is pressurized at the sametime (or nearly the same time) that the spring pocket 88 is beingexhausted.

Similarly, during a transition from the “01” state to the “10” state,the solenoid 108 is actuated and the solenoid 110 is deactuated. As aresult, the spring pocket 88 of the shift valve 52 is pressurized at thesame time (or nearly the same time) that the valve head 84 is beingexhausted. Also, the valve head 82 of the shift valve 50 is pressurizedat the same time (or nearly the same time) that the spring pocket 86 isbeing exhausted.

The fast valve actuation system 48 thereby provides a fast, butsequential, stroking and destroking of the shift valves 50, 52. As shownin FIG. 4, the time required for the shift valves 50, 52 to changestates sequentially is less than about 0.08 seconds (as illustrated, inthe range of about 0.07 seconds), according to experimental data. In thegraph, the line 130 represents the position of the shift valve 52 overtime, the line 132 represents the output pressure of theelectro-hydraulic actuator 110 over time, the line 134 represents theposition of the shift valve 50 over time, and the line 136 representsthe output pressure of the electro-hydraulic actuator 108 over time. Theline 138 represents the destroke time of the shift valve 52, which isless than 0.04 seconds as shown. The time required to stroke the shiftvalve 50 is similarly less than 0.04 seconds (as illustrated, in therange of about 0.03 seconds).

The fast sequential actuation of the shift valves 50, 52 reduces thepossibility of an indeterminate valve state (e.g. a state in which oneor both of the shift valves 50, 52 are partially stroked or both of theshift valves 50, 52 are fully stroked at the same time).

The fast valve actuation system 48 can be applied to situations in whicha pair of shift valves are used for transmission control. FIGS. 5A, 5B,5C and FIG. 6 illustrate one such application, in which the fast valveactuation system 48 is used in a hydraulic control circuit 28 for atransmission 12. In the illustrations, the transmission 12 is atransmission that has a ratio varying unit of the toroidal tractiontype. Transmissions of this type are available from TorotrakDevelopment, Ltd. of Lancashire, United Kingdom, for example.

Transmissions of the type illustrated in FIG. 5A may be referred to by anumber of different terms, including continuously variabletransmissions, infinitely variable transmissions, toroidaltransmissions, continuously variable transmissions of the full toroidalrace-rolling traction type, or similar terminology. In this disclosure,for ease of discussion, the term “continuously variable transmission” isused to refer to any of those types of transmissions in which ratios maybe controlled by a ratio varying unit, alternatively or in addition tobeing controlled by a set of gears that provide fixed, stepped ratios.

Referring to FIG. 5A, the transmission 12 is shown in the context of avehicle power train. A vehicle drive unit 10 outputs torque to atransmission input shaft 18. The drive unit 10 includes an internalcombustion engine, such as a spark-ignited engine or diesel engine, anengine-electric motor combination, or the like.

The transmission input shaft 18 connects the drive unit 10 to thetransmission 12. The transmission 12 uses a ratio varying unit(“variator”) 24 to provide a continuous variation of transmission ratio.The variator 24 is coupled between the transmission input shaft 18 andthe transmission output shaft 20 via gearing 22 and one or more clutches26. In general, the linkages 32, 34, 36 represent the mechanicalconnections between these components of the transmission 12, as will beunderstood by those skilled in the art. The linkage 36 is representativeof a variator output shaft.

FIGS. 5B and 5C illustrate components of the variator 24. Inside thevariator 24, there is a pair of disks 21, 23. The input disk 21 iscoupled to and driven by the transmission input shaft 18, while theoutput disk 23 is coupled to the variator output shaft 36. The spacebetween the inner surfaces 29, 31 of the disks 21, 23 forms a hollowdoughnut shape or ‘toroid.’ A number of rollers 25, 27 are positionedwithin the toroidal space defined by the surfaces 29, 31. The rollers25, 27 transmit drive from the input disk 21 to the output disk 23 via atraction fluid (not shown).

Each of the rollers 25, 27 is coupled to a hydraulic actuator 35 by acarriage 33. The hydraulic pressure in the actuators 35 is adjusted bythe variator control circuit 28 as described below with reference toFIG. 2. Varying the pressures in the actuators 35 changes the forceapplied by the actuators 35 to their respective rollers, to create arange of torque within the variator 24. The rollers 25, 27 are capableof translational motion and also rotate about a tilt axis relative tothe variator disks 21, 23. The force applied by the hydraulic actuators35 is balanced by a reaction force resulting from the torquestransmitted between the surfaces of the variator disks and the rollers.The end result is that in use, each roller moves and precesses to thelocation and tilt angle required to transmit a torque determined by theforce applied by the hydraulic actuators. FIG. 5C shows an example ofthe rollers 25, 27 positioned at a tilt angle relative to the surfaces29, 31, with the actuators 35 omitted for clarity.

In one illustrative implementation, the variator 24 is of the fulltoroidal type. In such implementation, the variator 24 includes twopairs of input and output disks 21, 23, and there are three rollerspositioned in the toroidal space defined by the disks of each pair, fora total of six rollers. Each roller is coupled to a hydraulic actuator35, for a total of six hydraulic actuators. These additional disks,rollers, and actuators are omitted from the drawings for clarity.

Alternative embodiments of the variator 24 may include a lesser orgreater number of disks, rollers, and/or actuators. In one suchembodiment, one hydraulic actuator is used to control all of therollers. In another embodiment, a compact lever arrangement is used inplace of the inline piston design shown in FIG. 5B. Moreover, someembodiments may use a partially toroidal rather than a full toroidalconfiguration.

Operation of the transmission 12 is controlled by an electro-hydrauliccontrol system 14. The electro-hydraulic control system 14 has avariator control circuit 28 and a clutch control circuit 30. In general,the linkages 38, 40, 42 represent the hydraulic fluid connectionsbetween components of the variator 24 and the variator control circuit28, between the clutch or clutches 26 and the clutch control circuit 30,and between the variator control circuit 28 and the clutch controlcircuit 30.

Aspects of the variator control circuit 28 are described below withreference to FIG. 6. Aspects of the clutch control circuit 30 are thesubject of U.S. Provisional Patent Application Ser. No. 61/287,031,filed Dec. 16, 2009, and U.S. Provisional Patent Application Ser. No.61/287,038, filed Dec. 16, 2009, both of which are incorporated hereinby this reference in their entirety.

Operation of the electro-hydraulic control system 14 is controlled bythe electronic control unit 16. In general, the linkages 44, 46represent the electrical connections between the electronic control unit16 and the electro-hydraulic control circuits 28, 30 of theelectro-hydraulic control system 14, as will be understood by thoseskilled in the art. The linkages 44, 46 may include insulated wiring,wireless links, or other suitable connections for exchanging data,communications and computer instructions. The electronic control unit 16includes computer circuitry configured to control the operation of thetransmission 12 based on inputs from various components of thetransmission 12. Such inputs may include digital and/or analog signalsreceived from sensors, controls or other like devices associated withthe vehicle components. The electronic control unit 16 processes inputsand parameters and issues electrical control signals to variouscomponents of the electro-hydraulic control system 14. The electroniccontrol unit 16 may be implemented as multiple separate logical orphysical structures or as a single unit, as will be appreciated by thoseskilled in the art.

The fast valve actuation system 48 is incorporated into the variatorcontrol circuit 28 as shown in FIG. 6. The variator control circuit 28applies a controlled force to the variator rollers by adjusting thepressures in the hydraulic actuators 35. As shown schematically in FIG.6, each of the hydraulic actuators 35 includes a pair of opposing faces70, 72, which are movable within their respective cylinders 74, 76. Eachof the opposing faces 70, 72 is exposed to hydraulic fluid pressure sothat the force applied by the actuator 35 to its respective roller isdetermined by the difference in the two pressures. Accordingly, theforce applied by the actuators 35 to the rollers has both a magnitudeand a direction. For example, the direction of the force may beconsidered positive if the face 70 receives greater pressure than theface 72 and negative if the face 72 receives greater pressure than theface 70, or vice versa. Illustratively, each of the hydraulic actuators35 includes a double-acting piston and cylinder arrangement.

The pressure applied to one side (e.g., the face 70) of the actuator 35is commonly referred to as “S1,” while the pressure applied to the otherside (e.g., the face 72) of the actuator 35 is commonly referred to as“S2.” The difference between the S1 and S2 pressures determines theforce applied by the actuators 35 to their respective rollers.

The actuators 35 and the fluid lines S1, S2 are configured to ensurethat the actuators 35 all react the same way, so that all of the rollers25 of the variator 24 are continuously maintained at the same pressuredifferential. A “higher pressure wins” valve 78 connects whichever ofthe two lines S1, S2 is at a higher pressure to an end load arrangement80.

The variator control circuit 28 adjusts the pressures in the lines S1,S2. A source of hydraulic fluid (i.e., a sump) 68 supplies fluid to apump 66. Electronically-controlled valves 60, 62, 64 regulate the fluidpressure that is applied to the lines S1 and S2. The valve 64 is a typeof pressure control valve commonly referred to as a main modulatorvalve. The main modulator valve 64 modulates the fluid pressureaccording to a predetermined desired pressure level for the variatorcontrol circuit 28. The valves 60, 62 are trim valves. The valve 60controls the application of fluid pressure to the line S1 through theshift valve 50, and the valve 62 controls the application of fluidpressure to the line S2 through the shift valve 52.

The position of the shift valve 50 determines whether or not the trimvalve 60 supplies fluid pressure to the line S1, and the position of theshift valve 52 determines whether or not the trim valve 62 suppliesfluid pressure to the line S2. The trim valve 60 is in fluidcommunication with the line S1 when the shift valve 50 is destroked, asshown in FIGS. 1 and 3. The trim valve 62 is in fluid communication withthe line S2 when the shift valve 52 is destroked, as shown in FIGS. 1and 2.

The fast valve actuation system 48 is coupled between the trim valves60, 62 and the rest of the variator control circuit 28. The fast valveactuation system 48 has its own fluid circuit 56 and fluid supply 54.The fluid circuit 56 includes the passages 90, 92, which fluidly couplethe respective valve heads and spring pockets of the shift valves 50, 52to one another as described above. In the variator control circuit 28,the fluid circuit 56 allows the fluid pressure from either the trimsystem 60 or the trim system 62 to be quickly blocked by quicklychanging the position of the shift valves 50, 52.

In the above-described application, the fast valve actuation system 48may be implemented as a protective measure intended to prevent anunintentional change in torque direction. The fast valve actuationsystem 48 may also allow the transmission to quickly respond tointentional changes in torque direction. For example, if the electroniccontrol unit 16 detects a shift into reverse commanded by the vehicleoperator, the electronic control unit 16 may send control signals to theelectro-hydraulic actuators 108, 110 as needed to quickly change thestate of the shift valves 50, 52.

A multiple-mode continuously variable ratio transmission has at leasttwo operating modes (e.g. low and high). Each mode is selected by aclutch that is engaged by the application of hydraulic fluid pressure ascontrolled by the transmission's control unit. Once the transmission isshifted into a given mode, then the transmission ratio is variable ascontrolled by the variator. The transition from one mode to another is asynchronous shift in which two clutches are applied, momentarily, at thesame time.

One such multiple-mode continuously variable ratio transmission hasthree modes of operation (e.g., M1, M2, M3), with each mode beingcontrolled by a separate clutch (e.g., C1, C2, C3). In mode M1, forwardor reverse launch and speeds up to about 10 miles per hour are possible.In mode M2, speeds in the range of about 10-30 miles per hour arepossible, in the forward direction. In mode M3, speeds in the range ofabout 30 miles per hour or higher are possible, in the forwarddirection.

The transmission is in mode M1 when the C1 clutch is applied, and inmode M2 when the C2 clutch is applied, and in mode M3 when the C3 clutchis applied. The transition from one mode to another thus requires one ofthe clutches to be released and another of the clutches to be applied.Aspects of the clutch control circuit 30 for such a three-modecontinuously variable ratio transmission are described in theaforementioned U.S. Provisional Patent Application Ser. Nos. 61/287,031and 61/287,038.

At the same time as clutches are being applied and released, thevariator control circuit 28 controls the variator ratio. During atransition from one of the modes M1, M2, M3 to another mode, thevariator ratio must be such that it allows for (or does not interferewith) the application and release of the appropriate clutches C1, C2,C3. The fast valve actuation system 48 may be used as a preventivemeasure against undesirable or unintended changes in the variator ratiowhile mode transitions are taking place.

Additionally, while the transmission is operating normally in one of themodes M1, M2, M3, the fast valve actuation system 48 may be used asdescribed above to quickly correct a change in torque direction that hasoccurred in error.

The present disclosure describes patentable subject matter withreference to certain illustrative embodiments. The drawings are providedto facilitate understanding of the disclosure, and may depict a limitednumber of elements for ease of explanation. Except as may be otherwisenoted in this disclosure, no limits on the scope of patentable subjectmatter are intended to be implied by the drawings. Variations,alternatives, and modifications to the illustrated embodiments may beincluded in the scope of protection available for the patentable subjectmatter.

What is claimed is:
 1. A system for a transmission, the systemcomprising: a variable-ratio unit, a hydraulic circuit fluidly coupledto the variable-ratio unit, the hydraulic circuit including a firstfluid chamber pressurizable to apply a first torque transmittingmechanism of the variable-ratio unit, a second fluid chamberpressurizable to apply a second torque transmitting mechanism of thevariable-ratio unit, a first shift valve fluidly coupled to the firstfluid chamber to selectively direct fluid pressure to the first fluidchamber, the first shift valve having a first valve head and a firstspring chamber axially spaced from the first valve head, a firstelectro-hydraulic actuator fluidly coupled to the first valve head ofthe first shift valve and actuatable by electrical signals to outputfluid pressure thereto, a second shift valve fluidly coupled to thesecond fluid chamber to selectively direct fluid pressure to the secondfluid chamber, the second shift valve including a second valve head anda second spring chamber axially spaced from the second valve head, and afirst fluid passage that fluidly couples the first valve head of thefirst shift valve directly to the second spring chamber of the secondshift valve, wherein the first electro-hydraulic actuator is selectivelycoupled to the second spring chamber through the first valve head andthe first fluid passage, and an electronic control unit coupled to thehydraulic circuit, the electronic control unit including computercircuitry configured to (i) detect a change in torque direction and (ii)actuate the first electro-hydraulic actuator to output fluid pressure tothe first valve head to stroke the first shift valve and destroke thesecond shift valve in rapid succession in response to the detectedchange in torque direction so that the second fluid chamber is connectedto fluid pressure and the first fluid chamber is disconnected from fluidpressure in rapid succession.
 2. The system of claim 1, wherein thehydraulic circuit includes (i) a second electro-hydraulic actuatorfluidly coupled to the second valve head of the second shift valve andactuatable by electrical signals to output fluid pressure thereto, and(ii) a second fluid passage separate from the first fluid passage thatfluidly couples the second valve head of the second shift valve directlyto the first spring chamber of the first shift valve.
 3. The system ofclaim 2, wherein the second electro-hydraulic actuator is selectivelycoupled to the first spring chamber through the second valve head andthe second fluid passage.
 4. The system of claim 2, wherein the firstand second fluid passages do not intersect with each other.
 5. Thesystem of claim 1, wherein the computer circuitry is configured todirect the first electro-hydraulic actuator to substantiallysimultaneously output fluid pressure to the first valve head of thefirst shift valve and the first fluid passage.
 6. The system of claim 1,wherein the first and second torque transmitting mechanisms are variatordisk actuators.
 7. The system of claim 1, wherein the first and secondtorque transmitting mechanisms are clutches.
 8. The system of claim 1,wherein (i) the transmission is operable in at least three differentforward operating modes, and (ii) the computer circuitry is configuredto detect the change in torque direction in one of the forward operatingmodes.
 9. The system of claim 1, wherein (i) the transmission isoperable in at least three different forward operating modes, and (ii)the computer circuitry is configured to detect the change in torquedirection during a transition from one of the forward operating modes toanother of the forward operating modes.
 10. A system for a transmission,the system comprising: a variable-ratio unit including a first torquetransmitting mechanism and a second torque transmitting mechanism, avalve assembly actuatable to selectively connect a first fluid chambercoupled to the first torque transmitting mechanism to fluid pressure anddisconnect a second fluid chamber coupled to the second torquetransmitting mechanism from fluid pressure in rapid succession, thevalve assembly including a first shift valve having a first valve headand a first spring chamber axially spaced from the first valve head, afirst electro-hydraulic actuator fluidly coupled to the first valve headof the first shift valve and actuatable by electrical signals to outputfluid pressure thereto, a second shift valve having a second valve headand a second spring chamber axially spaced from the second valve head,and a second electro-hydraulic actuator fluidly coupled to the secondvalve head of the second shift valve and actuatable by electricalsignals to output fluid pressure thereto, and an electronic control unitcoupled to the valve assembly, the electronic control unit includingcomputer circuitry configured to (i) de-actuate the firstelectro-hydraulic actuator so that fluid pressure is directed throughthe first shift valve to the first fluid chamber to apply the firsttorque transmitting mechanism and actuate the second electro-hydraulicactuator to apply fluid pressure to the second valve head and connectthe second electro-hydraulic actuator to the first spring chamber of thefirst shift valve through the second valve head, (ii) detect a change intorque direction, and (iii) stroke the first shift valve and destrokethe second shift valve in rapid succession in response to the detectedchange in torque direction.
 11. The system of claim 10, wherein (i) thecomputer circuitry is configured to actuate the first electro-hydraulicactuator to apply fluid pressure to the first valve head of the firstshaft valve, connect the first electro-hydraulic actuator to the secondspring chamber of the second shift valve through the first valve head,and disconnect the first fluid chamber from fluid pressure to stroke thefirst shift valve, and (ii) the computer circuitry is configured tode-actuate the second electro-hydraulic actuator to remove fluidpressure from the second valve head of the second shift valve,disconnect the second electro-hydraulic actuator from the first springchamber of the first shift valve, and direct fluid pressure through thesecond shift valve to the second fluid chamber to apply the secondtorque transmitting mechanism to destroke the second shift valve. 12.The system of claim 11, wherein the computer circuitry is configured tode-actuate the first electro-hydraulic actuator to couple a firstpressure control valve to the first fluid chamber.
 13. The system ofclaim 12, wherein the computer circuitry is configured to de-actuate thesecond electro-hydraulic actuator to couple a second pressure controlvalve to the second fluid chamber.
 14. The system of claim 13, whereinthe computer circuitry is configured to actuate the secondelectro-hydraulic actuator to couple the second fluid chamber to a thirdpressure control valve.
 15. The system of claim 10, wherein the computercircuitry is configured to stroke the first shift valve and destroke thesecond shift valve in rapid succession in response to the detectedchange in torque direction in less than about 0.08 seconds.
 16. Thesystem of claim 10, wherein the first and second torque transmittingmechanisms are variator disk actuators.
 17. The system of claim 10,wherein (i) the transmission is operable in at least three differentforward operating modes, and (ii) the computer circuitry is configuredto detect the change in torque direction in one of the forward operatingmodes.
 18. The system of claim 10, wherein (i) the transmission isoperable in at least three different forward operating modes, and (ii)the computer circuitry is configured to detect the change in torquedirection during a transition from one of the forward operating modes toanother of the forward operating modes.